There has been significant recent interest in the development of terahertz (THz) integrated circuits (ICs) and detectors based upon two-dimensional electron gas (2DEG) systems in semiconductor nanostructures and graphene. Because microwave and THz fields coupled to a 2DEG excite plasma waves, plasmon-based field-effect devices can operate well above fT, the cutoff frequency determined by carrier transit times. See M. I. Dyakonov and M. S. Shur, Phys. Rev. Lett. 71, 2465 (1993); M. I. Dyakonov and M. S. Shur, IEEE Trans. on Electron Devices 43, 380 (1996); W. F. Andress et al., Nano Lett. 12, 2272 (2012); P. J. Burke et al., Appl. Phys. Lett. 76, 745 (2000); and M. J. W. Rodwell et al., IEEE Trans. on Electron Devices 48, 2606 (2001). Overdamped plasmonic field-effect transistors (FETs) have been fabricated from III-V, Si, and graphene material systems and utilized for room temperature THz detection. See D. Coquillat et al., Opt. Express 18, 6024 (2010); S. Preu et al., IEEE Trans. on THz Sci. and Tech. 2, 278 (2012); M. S. Vitiello et al., Nano Lett. 12, 96 (2011); A. D. Gaspare et al., Appl. Phys. Lett. 100, 203504 (2012); A. Pitanti et al., Appl. Phys. Lett. 101, 141103 (2012); A. Lisauskas et al., J. Appl. Phys. 105, 114511 (2009); S. Boppel et al., Electronics Letters 47, 661 (2011); and L. Vicarelli et al., Nature Mater. 11, 865 (2012). To exploit underdamped two-dimensional (2D) plasmons in III-V heterostructures, cryogenic operation of a high-electron-mobility-transistor (HEMT) is generally required. See W. F. Andress et al., Nano Lett. 12, 2272 (2012); P. J. Burke et al., Appl. Phys. Lett. 76, 745 (2000); X. G. Peralta et al., Appl. Phys. Lett. 81, 1627 (2002); E. A. Shaner et al., Appl. Phys. Lett. 87, 193507 (2005); W. Knap et al., Appl. Phys. Lett. 81, 4637 (2002); and V. M. Muravev and I. V. Kukushkin, Appl. Phys. Lett. 100, 082102 (2012). Within this constraint, potential applications such as THz plasmonic ICs and detectors based on III-V heterostructures can be realized in these material systems. However, as the quality of large-area graphene materials improves, similar devices may emerge that operate in the mid-infrared at room temperature.